You can star messages to indicate that they're important to you. To mark a conversation with a star, click its star icon in the conversation list. You can star an individual message by clicking the star at the upper right of the message itself.

Starred messages appear in the Starred folder in the folder list.

Geary marks messages as read automatically as you read them. To mark one or more conversations as unread, select the conversations(s), then select Mark as Unread from the Mark menu on the toolbar. To mark an individual message as unread, select Mark as Unread from the message menu at the upper right of the message.

To mark an individual message as read, you may select Mark as Read from the dropdown menu .